Issue 3 16k internal RAM mod

Discussions about Sinclair ZX80 and ZX81 Hardware
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sirmorris
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Re: Issue 3 16k internal RAM mod

Post by sirmorris » Wed Jul 26, 2017 8:52 am

Pokemon made a RAM expansion which altered one of the first instructions of the ROM to start counting mem at +32k. It was genius. Making it count less (i.e. 1k) would be harder as you'd need to affect multiple bits IIUIC.

If you have an internal RAM, why not swap the ROM out - then you're in control of how the mem check works. You could have multiple images and a switch. I guess we're veering off into überzeddy territory now, though.
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Lardo Boffin
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Re: Issue 3 16k internal RAM mod

Post by Lardo Boffin » Wed Jul 26, 2017 4:37 pm

Certainly somewhat beyond my abilities! :shock:
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gammaray
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Re: Issue 3 16k internal RAM mod

Post by gammaray » Thu Jul 27, 2017 1:01 am

Here, Here!
If you have an internal RAM, why not swap the ROM out - then you're in control of how the mem check works. You could have multiple images and a switch.
As I have always said make modifications that are switchable to stock operation if they are not otherwise transparent.

Just sayin'

Upon closer look, I guess you meant switching ROMs not disabling mod
Last edited by gammaray on Sat Dec 23, 2017 6:53 pm, edited 1 time in total.
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mooredan
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Re: Issue 3 16k internal RAM mod

Post by mooredan » Sat Dec 23, 2017 1:45 am

Kind of late to the party, but here's another completed mod (click on image for full size):

Image

Image

No problem at all, here's the output of "PRINT PEEK 16388 + 256 * PEEK 16389" a.k.a. RAMTOP

Image

That's 32768 -- I've got to get me a bigger monitor.....
Dan Moore
Portland, Oregon, USA

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